The present invention relates to a film scanner capable of capturing images formed on silver-salt films.
Recently, as personal computers become widespread, images are captured to generate image data, and a personal computer is used for processing or recording captured electronic images (i.e., the image data). Conventionally, a scanner and a digital camera have been used for capturing images. It has been desired that the images formed on a silver-salt film are captured. Conventionally, for capturing images printed on photographic papers, a scanner has been used. However, the scanner cannot capture the images formed on the film directly.
In order to capture images on the film directly, a film scanner has been developed. As the conventional scanner does, the film scanner has a CCD line sensor which receives light passed through the film. The image is scanned in a predetermined direction (i.e., a main scanning direction) in which the line sensor extends, while a table on which the film is mounted is slid relative to the line sensor in a direction (i.e., an auxiliary scanning direction) perpendicular to the main scanning direction, thereby a two-dimensional area is scanned.
In such a film scanner, it is sometimes required to capture images at a plurality of scanning resolutions. For example, a prescanning may be executed to confirm the scanning area before a normal scanning (i.e., a principal scanning) for capturing the image is executed. The scanning resolution of prescanning need not be as high as that of the normal scanning. Generally, when the scanning resolution is higher, the longer time is required for scanning. Therefore, it is preferable that a prescanning is executed at a lower resolution in order to reduce the time for scanning. In order to lower the resolution in the above-described film scanner, the pitch in the auxiliary direction may be enlarged. For enlarging the pitch in prescanning, in a conventional film scanner, the rotating rate of the motor for sliding the table could be increased. However, in order to implement such control in the conventional film scanner, the structure as well as the control circuits of the motor would be complicated.
In another conventional film scanner, when the prescanning is performed, the scanning of the image in the auxiliary direction is executed at every predetermined intervals, without increasing the rotating speed of the motor. Such control, however, does not reduce the time required for prescanning although the scanning pitch in the auxiliary scanning direction is enlarged.
It is therefore an object of the invention to provide an improved film scanner capable of performing a prescanning faster than a normal scanning, without complicating the structure thereof.
For the above object, according to the present invention, there is provided a film scanner for scanning an image formed on a film, which is provided with a line sensor that scans the image in a main scanning direction, a table supporting the film, the table being slidable forwardly and reversely in an auxiliary scanning direction that is perpendicular to the main scanning direction, a driving source generating a driving force, a table driving mechanism that drives the table in the auxiliary scanning direction, and a geared transmission that receives the driving force of the driving source and outputs, to the table driving mechanism, one of a first and a second driving force. The first driving force is a force with which the table driving mechanism drives the table in a forward direction at a first speed, and the second driving force is a force with which the table driving mechanism drives the table in a reverse direction at a second speed that is different from the first speed.
With this configuration, the driving force of the driving source is converted into a movement at a first speed or a second speed. Therefore, a time period required for scanning can be reduced when scanned at the first speed than the second speed.
Preferably, the drive source includes a stepping motor.
Optionally, the geared transmission including a planet clutch, which is provided with a sun gear secured to a driving shaft of the stepping motor, first and second planet gears meshing with the sun gear. The first and second planet gears are rotatable around the sun gear in association with the rotation of the sun gear. The planet clutch is further provided with first and second driven gears, the first and second driven gears having different numbers of teeth. The first planet gear meshes with the first driven gear when the sun gear rotates forwardly, and the second planet gear meshes with the second driven gear when the sun gear rotates reversely.
Preferably, when the first planet gear meshes with the first driven gear, the second planet gear is disengaged from the second driven gear, and when the second planet gear meshes with the second driven gear, the first planet gear is disengaged from the first driven gear.
In particular, the planet clutch has a rotatable arm rotatably supported by the driving shaft of the stepping motor. The rotatable arm extends in a radial direction of the sun gear, and the first and second planet gears are rotatably supported at end portions of the rotatable arm.
Optionally, the table driving mechanism includes a rack and pinion mechanism. The pinion, the first driven gear and the second driven gear are integrally formed and rotatable coaxially. The rack formed on one surface of the table, the rack meshing with the pinion.
Further optionally, the film scanner further includes a film holder in which the film is inserted, the film holder being slidably supported on the table so that a desired frame of the image formed on the film could be scanned.
Still optionally, the first speed is greater than the second speed.
Preferably, scanning at a lower resolution is performed when the first planet gear meshes with the first driven gear, and scanning at a higher resolution is performed when the second planet gear meshes with the second driven gear.
In particular, prescanning is performed when the first planet gear meshes with the first driven gear, and principal scanning is performed when the second planet gear meshes with the second driven gear.